Ejectors

ABSTRACT

An ejector has: a motive flow inlet; a secondary flow inlet; an outlet; and a motive nozzle. The motive nozzle has an exit. A motive flow flowpath proceeds through the motive nozzle and joins a secondary flow flowpath extending from the secondary flow inlet to form a combined flowpath to the outlet. From upstream to downstream along the motive flow flowpath, the motive nozzle has: a convergent section; a throat; a first divergent section commencing within 10% of a throat-to-exit length and diverging over a first length (L D1 ) of at least 10% of the throat-to-exit length (L TE ); a second divergent section, the second divergent section diverging over a second length (L D2 ) of at least 10% of the throat-to-exit length at a shallower angle than the first divergent section over said first length.

CROSS-REFERENCE TO RELATED APPLICATION

Benefit is claimed of U.S. Patent Application No. 62/162,618, filed May15, 2015, and entitled “Ejectors”, the disclosure of which isincorporated by reference herein in its entirety as if set forth atlength.

BACKGROUND

The present disclosure relates to refrigeration. More particularly, itrelates to ejector refrigeration systems.

Earlier proposals for ejector refrigeration systems are found in U.S.Pat. No. 1,836,318 and U.S. Pat. No. 3,277,660. FIG. 1 shows one basicexample of an ejector refrigeration system 20. The system includes acompressor 22 having an inlet (suction port) 24 and an outlet (dischargeport) 26. The compressor and other system components are positionedalong a refrigerant circuit or flowpath 27 and connected via variousconduits (lines). A discharge line 28 extends from the outlet 26 to theinlet 32 of a heat exchanger (a heat rejection heat exchanger in anormal mode of system operation (e.g., a condenser or gas cooler)) 30. Aline 36 extends from the outlet 34 of the heat rejection heat exchanger30 to a primary inlet (liquid or supercritical or two-phase inlet) 40 ofan ejector 38. The ejector 38 also has a secondary inlet (saturated orsuperheated vapor or two-phase inlet) 42 and an outlet 44. A line 46extends from the ejector outlet 44 to an inlet 50 of a separator 48. Theseparator has a liquid outlet 52 and a gas or vapor outlet 54. A suctionline 56 extends from the gas outlet 54 to the compressor suction port24. The lines 28, 36, 46, 56, and components therebetween define aprimary loop 60 of the refrigerant circuit 27. A secondary loop 62 ofthe refrigerant circuit 27 includes a heat exchanger 64 (in a normaloperational mode being a heat absorption heat exchanger (e.g.,evaporator)). The evaporator 64 includes an inlet 66 and an outlet 68along the secondary loop 62. An expansion device 70 is positioned in aline 72 which extends between the separator liquid outlet 52 and theevaporator inlet 66. An ejector secondary inlet line 74 extends from theevaporator outlet 68 to the ejector secondary inlet 42.

In the normal mode of operation, gaseous refrigerant is drawn by thecompressor 22 through the suction line 56 and inlet 24 and compressedand discharged from the discharge port 26 into the discharge line 28. Inthe heat rejection heat exchanger, the refrigerant loses/rejects heat toa heat transfer fluid (e.g., fan-forced air or water or other fluid).Cooled refrigerant exits the heat rejection heat exchanger via theoutlet 34 and enters the ejector primary inlet 40 via the line 36.

The exemplary ejector 38 (FIG. 2) is formed as the combination of amotive (primary) nozzle 100 nested within an outer member 102. Theprimary inlet 40 is the inlet to the motive nozzle 100. The outlet 44 isthe outlet of the outer member 102. The primary refrigerant flow (motiveflow) 103 enters the inlet 40 and then passes into a convergent section104 of the motive nozzle 100. It then passes through a throat section106 and an expansion (divergent) section 108 through an outlet (exit)110 of the motive nozzle 100. The motive nozzle 100 accelerates the flow103 and decreases the pressure of the flow. The secondary inlet 42 formsan inlet of the outer member 102. The pressure reduction caused to theprimary flow by the motive nozzle helps draw the secondary flow 112 intothe outer member. The outer member includes a mixer having a convergentsection 114 and an elongate throat or mixing section 116. The outermember also has a divergent section or diffuser 118 downstream of theelongate throat or mixing section 116. The motive nozzle outlet 110 ispositioned within the convergent section 114. As the flow 103 exits theoutlet 110, it begins to mix with the flow 112 with further mixingoccurring through the mixing section 116 which provides a mixing zone.Thus, respective primary and secondary flowpaths extend from the primaryinlet and secondary inlet to the outlet, merging at the exit. Inoperation, the primary flow 103 may typically be supercritical uponentering the ejector and subcritical upon exiting the motive nozzle. Thesecondary flow 112 is gaseous (or a mixture of gas with a smaller amountof liquid) upon entering the secondary inlet port 42. The resultingcombined flow 120 is a liquid/vapor mixture and decelerates and recoverspressure in the diffuser 118 while remaining a mixture. Upon enteringthe separator, the flow 120 is separated back into the flows 103 and112. The flow 103 passes as a gas through the compressor suction line asdiscussed above. The flow 112 passes as a liquid to the expansion valve70. The flow 112 may be expanded by the valve 70 (e.g., to a low quality(two-phase with small amount of vapor)) and passed to the evaporator 64.Within the evaporator 64, the refrigerant absorbs heat from a heattransfer fluid (e.g., from a fan-forced air flow or water or otherliquid) and is discharged from the outlet 68 to the line 74 as theaforementioned gas.

Use of an ejector serves to recover pressure/work. Work recovered fromthe expansion process is used to compress the gaseous refrigerant priorto entering the compressor. Accordingly, the pressure ratio of thecompressor (and thus the power consumption) may be reduced for a givendesired evaporator pressure. The quality of refrigerant entering theevaporator may also be reduced. Thus, the refrigeration effect per unitmass flow may be increased (relative to the non-ejector system). Thedistribution of fluid entering the evaporator is improved (therebyimproving evaporator performance). Because the evaporator does notdirectly feed the compressor, the evaporator is not required to producesuperheated refrigerant outflow. The use of an ejector cycle may thusallow reduction or elimination of the superheated zone of theevaporator. This may allow the evaporator to operate in a two-phasestate which provides a higher heat transfer performance (e.g.,facilitating reduction in the evaporator size for a given capability).

The exemplary ejector may be a fixed geometry ejector or may be acontrollable ejector. FIG. 2 shows controllability provided by a needlevalve 130 having a needle 132 and an actuator 134. The actuator 134shifts a tip portion 136 of the needle into and out of the throatsection 106 of the motive nozzle 100 to modulate flow through the motivenozzle and, in turn, the ejector overall. Exemplary actuators 134 areelectric (e.g., solenoid or the like). The actuator 134 may be coupledto and controlled by a controller 140 which may receive user inputs froman input device 142 (e.g., switches, keyboard, or the like) and sensors(not shown). The controller 140 may be coupled to the actuator and othercontrollable system components (e.g., valves, the compressor motor, andthe like) via control lines 144 (e.g., hardwired or wirelesscommunication paths). The controller may include one or more:processors; memory (e.g., for storing program information for executionby the processor to perform the operational methods and for storing dataused or generated by the program(s)); and hardware interface devices(e.g., ports) for interfacing with input/output devices and controllablesystem components.

A further variation is shown in Ogata et al. U.S. Pat. No. 8,523,091,Sep. 3, 2013. Ogata et al. shows an ejector with a motive nozzle havinga convergent section leading to at least three distinct divergentsections. An intermediate section of the three has a shallower taperthan the other two sections.

SUMMARY

One aspect of the disclosure involves an ejector comprising: a motiveflow inlet; a secondary flow inlet; an outlet; and a motive nozzle. Themotive nozzle has an exit. A motive flow flowpath proceeds through themotive nozzle and joins a secondary flow flowpath extending from thesecondary flow inlet to form a combined flowpath to the outlet. Fromupstream to downstream along the motive flow flowpath, the motive nozzlehas: a convergent section; a throat; a first divergent sectioncommencing within 10% of a throat-to-exit length and diverging over afirst length of at least 10% of the throat-to-exit length (L_(TE)); asecond divergent section, the second divergent section diverging over asecond length (LD2) of at least 10% of the throat-to-exit length at ashallower angle than the first divergent section over said first length.

In one or more embodiments of the other embodiments, along the motiveflow flowpath: the first divergent section extends at a single firsthalf-angle (θ_(D1)) directly from the throat; and the second divergentsection extends at a single second half-angle (θ_(D2)) directly from thefirst divergent section.

In one or more embodiments of the other embodiments, the firsthalf-angle is 1.0° to 4.0°; and the second half-angle is 0.7° to 3.0°.

In one or more embodiments of the other embodiments, the firsthalf-angle is 1.5° to 2.5°; and the second half-angle is 0.8° to 1.5°.

In one or more embodiments of the other embodiments, the secondhalf-angle is 30% to 80% of the first angle.

In one or more embodiments of the other embodiments, the secondhalf-angle is 40% to 60% of the first angle.

In one or more embodiments of the other embodiments, the first length isat least 50% of the throat-to-exit length; and the second length is atleast 15% of the throat-to-exit length

In one or more embodiments of the other embodiments, the seconddivergent section ends within 5% of the throat-to-exit length from theexit.

In one or more embodiments of the other embodiments, a convergentsection length (L_(C)) is greater than the throat-to-exit length.

In one or more embodiments of the other embodiments, the convergentsection length is at least 110% of the throat-to-exit length.

In one or more embodiments of the other embodiments, the motive nozzleis metallic.

In one or more embodiments of the other embodiments: there is only asingle said motive flow inlet; there is only a single said secondaryflow inlet; and there is only a single said outlet.

Another aspect of the disclosure involves a method for using theejector. The method comprises: passing a motive flow through the motiveflow inlet; passing a secondary flow through the secondary flow inlet;merging the motive flow and the secondary flow to form a merged flow;and passing the merged flow through the outlet. The motive flow reachesa first Mach number of 0.9 to 1.2 at a downstream end of the firstdivergent section. The motive flow accelerates to a second Mach numberof at least 0.05 greater than the first Mach number in the seconddivergent section.

In one or more embodiments of the other embodiments, the second Machnumber is at least 0.2 greater than the first Mach number.

In one or more embodiments of the other embodiments, a vapor compressionsystem comprises the ejector.

In one or more embodiments of the other embodiments, the vaporcompression system further comprises: a compressor; a first heatexchanger; a second heat exchanger; and a separator having: an inlet; aliquid outlet; and a vapor outlet; an expansion device.

In one or more embodiments of the other embodiments, the vaporcompression system further comprises: a plurality of conduits positionedto define a first flowpath sequentially through: the compressor; thefirst heat exchanger; the ejector from the motive flow inlet through theejector outlet; and the separator, and then branching into: a firstbranch returning to the compressor; and a second branch passing throughthe expansion device and second heat exchanger to the secondary inlet.

Another aspect of the disclosure involves an ejector comprising: amotive flow inlet; a secondary flow inlet; an outlet; and a motivenozzle. The motive nozzle has an exit. A motive flow flowpath proceedsthrough the motive nozzle and joins a secondary flow flowpath extendingfrom the secondary flow inlet to form a combined flowpath to the outlet.From upstream to downstream along the motive flow flowpath, the motivenozzle has: a convergent section; a throat; and means for providing asecond acceleration upstream of the exit lower than a first accelerationdownstream of the throat.

In one or more embodiments of the other embodiments, the means comprisesa first divergent section and a second divergent section at a shallowerangle than the first divergent section.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a prior art ejector refrigeration system.

FIG. 2 is an axial sectional view of a prior art ejector.

FIG. 3 is an axial sectional view of a second ejector.

FIG. 4 is an axial sectional view of a motive nozzle of the secondejector.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 3 shows a modified ejector 200 that may replace the ejector of FIG.2 in the system of FIG. 1. However, the modification as described belowmay apply to other ejectors used in other vapor compression systems. Theejector 200 may represent a modification of a baseline ejector differingin terms of the interior of the motive nozzle 202. Various features thatmay be shared with the baseline FIG. 2 ejector are referenced withcorresponding numerals and are not necessarily separately discussed.

As with the baseline ejector, the nozzle 200 and its passageway comprisea convergent section 206 leading to a throat 208. The exemplary throatis a single longitudinal location (zero length). Alternative throats maybe represented by a cylindrical cross-section (e.g., a right circularcylinder) of non-zero length. Downstream of the throat (e.g.,immediately/directly downstream) is a first divergent section 210. Anexemplary first divergent section extends over a length L_(D1). Anexemplary first divergent section has a single angle of diversion (shownas a half-angle θ_(D1)).

A second divergent section 212 is downstream of the first divergentsection 210. The second divergent section is less divergent (smallermagnitude of an angle between the surface and the centerline or axis ofthe passageway) than the first divergent section. The second divergentsection may have a single constant divergence angle (shown as half-angleθ_(D2)) over a length L_(D2). The second divergent section can extenddirectly from the first divergent section to the exit so that the twolengths equal the throat-to-exit length L_(TE). For throats of non-zerolength, L_(TE) may be measured from the downstream end of the throat.With the addition of variations such as bevels and chamfers, the lengthof the two may sum to greater than or equal to 90% of L_(TE), forexample at least 95% or at least 98%.

In some embodiments, the angle θ_(D1) is from 0.5° to 5.0°, or 1.0 to4.0°, or 1.5° to 2.5°, or 2.0°. The angle θ_(D1) may be selected toprovide a rapid expansion/vaporization of the motive flow.

In some embodiments, the angle θ_(D2) is from 0.3° to 4.0°, or 0.7° to3.0°, or 0.8° to 1.5°, or 1.0° to 1.3°. This may be selected to tailorthe exit flow for improved mixing with the secondary flow. In someembodiments, the angle θ_(D2) is from 40% to 60% of θ_(D1), or 40% to70% of θ_(D1), or 30% to 80% of θ_(D1).

In some embodiments, the angle L_(D1) is 5% to 80% of L_(TE), or 10% to60%, or 20% to 40%. This may be selected to limit the Mach number ofmaterial flowing through the first divergent section 210 (e.g., thedownstream end thereof forming a junction with the second divergentsection 212) to a range of 0.9 to 1.2. The Mach number in the seconddivergent section 212 will be higher (e.g., 1.0 to 2.0 at the exit 110and at least 0.050 higher than in the first divergent section (e.g., atthe downstream end of the first divergent section), or at least 0.10higher, or at least 0.20 higher).

In some embodiments, the angle L_(D2) is 20% to 95% of L_(TE), or 40% to90%, or 60% to 80%. This may be selected to avoid flow separation andavoid a shock inside the nozzle.

In operation, high pressure (e.g., transcritical or liquid state), lowvelocity (e.g., Mach number of 0.01 to 0.1), flow enters the motivenozzle. It then undergoes acceleration to a Mach number of 0.8 to 1.0near the throat (minimum cross-section) location or region. Thereafter,the flow further accelerates in the first divergent section to a Machnumber of 0.9 to 1.2 at the end of the first divergent section. The flowfurther accelerates in the second divergent section to a Mach number of1.0 to 2.0 at the exit of the second divergent section. The Mach numberof the flow in the second divergent section (e.g., at the end of thesecond divergent section) is at least 0.05 higher than that in the firstdivergent section (e.g., at the end of the first divergent section). Invarious implementations, this may offer an advantageous combination ofsmooth flow acceleration and cost reduction (minimizing divergent anglesand optimal choice of angle relationships) because faster accelerationis first targeted in the first divergent section using a larger angle(than the second divergent section) and slower acceleration (with thehighest Mach number) is targeted in the second divergent section with asmaller angle (than the first divergent section).

Relative to a baseline nozzle with a single angle of divergence, one ormore advantages may be present in some particular implementations. Forexample, the first divergent section may quickly expand and vaporize themotive flow; whereas the second divergent section controls the fluidexiting angle and velocity which can improve the mixing process in themixer.

Relative to more complex configurations such as the third figure ofOgata et al. there may also be one or more of several advantages in someparticular implementations. One notable advantage is that animplementation with just two divergent angles may be easier to align thesections when manufacturing (e.g., allow for easier centering of theaxes of the throat, the first divergent section, and/or the seconddivergent section relative to any one of the preceding when machining).Second, reduced overall length may correspondingly reduce material costand/or reduce costs of the needle and its actuator if present.

A further potential advantage in some particular implementationsrelative to the Ogata et al. configuration involves the relationship ofthe convergent section length L_(C) to the total divergent sectionlength or throat-to-exit length L_(TE). Whereas Ogata et al. shows anextremely short convergent length, the present exemplary L_(C) may belarger than L_(D1) and L_(D2) individually and combined. For example,exemplary L_(C) may be at least 80% of L_(TE), at least, 100% of L_(TE),or at least 105% of L_(TE.)This relatively long convergent section canprovide benefits of smoothed flow transition in some particularimplementations. For example, flow through the convergent section mayhave a Mach number of 0.1 to 1.0 (e.g., entering the convergent sectionhaving a Mach number of 0.10 and exiting the convergent section having aMach number of 0.9 to 1.0), this relatively longer transition canprovide smother flow acceleration and thus reduced flow separation andhence reduced frictional or shear losses. The losses can be moresignificant at higher Mach numbers (e.g., at Mach numbers of 0.5 to1.0). A shorter convergent section may have a similar change in Machnumber over a shorter length, thus suffering greater flow separationfrictional and/or shear losses. A relatively longer convergent sectioncan be particularly beneficial for embodiments having needles extendinginto the convergent section. The presence of the needle can causeadditional flow disturbances in the convergent section as the flow isaccelerated.

In other variations, additional features such as those of other baselinenozzles may be present. For example, a non-zero length throat is notedabove. Furthermore, the use of various needles and their actuators arewithin the scope of the present disclosure and their use without doesnot depart from the spirit of the present disclosure.

Materials and manufacturing techniques commonly used for ejectors andvapor compression systems may be used. Motive nozzles can include metal(e.g., steel, aluminum, copper, titanium, or a combination including atleast one of the foregoing), plastic, or a combination comprising atleast one of the foregoing. Manufacturing techniques can includemachining (e.g., lathe turning of exterior surface portions of themotive nozzle and drilling or electro-discharge machining (EDM) of thecentral passageway from motive nozzle inlet to motive nozzle exit). Suchtechniques can yield a passageway (e.g., throat, convergent sectionand/or divergent section) centered on the nozzle axis (e.g., of circularcross-section). Exemplary forming of the passageway comprises end-to enddrilling. This may define the throat diameter. Then the divergentsection may be formed by EDM (e.g., wire EDM). An exemplary EDM of theconvergent section involves using a conical tool (electrode) shaped tothe profile of the convergent section Similarly, one or more electrodesmay be used to EDM the divergent sections (e.g., two conical electrodescorresponding to the respective divergent sections). In an embodiment,the ejector can be formed in an additive manufacturing process such as,but not limited to, powdered metal sintering, direct deposition, and thelike.

The use of “first”, “second”, and the like in the description andfollowing claims is for differentiation within the claim only and doesnot necessarily indicate relative or absolute importance or temporalorder. Similarly, the identification in a claim of one element as“first” (or the like) does not preclude such “first” element fromidentifying an element that is referred to as “second” (or the like) inanother claim or in the description.

One or more embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made. For example, whenapplied to an existing basic system, details of such configuration orits associated use may influence details of particular implementations.Accordingly, other embodiments are within the scope of the followingclaims.

1. An ejector comprising: a motive flow inlet; a secondary flow inlet;an outlet; a motive nozzle having an exit; and a motive flow flowpathproceeding through the motive nozzle and joining a secondary flowflowpath extending from the secondary flow inlet to form a combinedflowpath to the outlet, wherein from upstream to downstream along themotive flow flowpath, the motive nozzle has: a convergent section; athroat; a first divergent section commencing within 10% of athroat-to-exit length and diverging over a first length (L_(D1)) of atleast 10% of the throat-to-exit length (L_(TE)); and a second divergentsection, the second divergent section diverging over a second length(L_(D2)) of at least 10% of the throat-to-exit length at a shallowerangle than the first divergent section over said first length.
 2. Theejector of claim 1 wherein, along the motive flow flowpath: the firstdivergent section extends at a single first half-angle (θ_(D1)) directlyfrom the throat; and the second divergent section extends at a singlesecond half-angle (θ_(D2)) directly from the first divergent section. 3.The ejector of claim 2 wherein: the first half-angle is 1.0° to 4.0°;and the second half-angle is 0.7° to 3.0°.
 4. The ejector of either ofclaim 2 wherein: the first half-angle is 1.5° to 2.5°; and the secondhalf-angle is 0.8° to 1.5°.
 5. The ejector of either of claim 2 wherein:the second half-angle is 30% to 80% of the first angle.
 6. The ejectorof either of claim 2 wherein: the second half-angle is 40% to 60% of thefirst angle.
 7. The ejector of claim 1 wherein: the first length is atleast 50% of the throat-to-exit length; and the second length is atleast 15% of the throat-to-exit length
 8. The ejector of claim 1wherein: the second divergent section ends within 5% of thethroat-to-exit length from the exit.
 9. The ejector of claim 1 wherein:the motive nozzle is metallic.
 10. The ejector of claim 1 wherein: aconvergent section length (L_(C)) is greater than the throat-to-exitlength.
 11. The ejector of claim 10 wherein: the convergent sectionlength is at least 110% of the throat-to-exit length.
 12. The ejector ofclaim 1 wherein: there is only a single said motive flow inlet; there isonly a single said secondary flow inlet; and there is only a single saidoutlet.
 13. The ejector of claim 12 wherein: the motive nozzle ismetallic.
 14. A vapor compression system comprising the ejector ofclaim
 1. 15. The vapor compression system of claim 14 furthercomprising: a compressor; a first heat exchanger; a second heatexchanger; and a separator having: an inlet; a liquid outlet; and avapor outlet; an expansion device.
 16. The vapor compression system ofclaim 15 further comprising: a plurality of conduits positioned todefine a first flowpath sequentially through: the compressor; the firstheat exchanger; the ejector from the motive flow inlet through theejector outlet; and the separator, and then branching into: a firstbranch returning to the compressor; and a second branch passing throughthe expansion device and second heat exchanger to the secondary inlet.17. A method for using the ejector of claim 1 comprising: passing amotive flow through the motive flow inlet; passing a secondary flowthrough the secondary flow inlet; merging the motive flow and thesecondary flow to form a merged flow; and passing the merged flowthrough the outlet, wherein: the motive flow reaches a first Mach numberof 0.9 to 1.2 at a downstream end of the first divergent section; andthe motive flow accelerates to a second Mach number of at least 0.05greater than the first Mach number in the second divergent section. 18.The method of claim 17 wherein: the second Mach number is at least 0.2greater than the first Mach number.
 19. An ejector comprising: a motiveflow inlet; a secondary flow inlet; an outlet; a motive nozzle having anexit; and a motive flow flowpath proceeding through the motive nozzleand joining a secondary flow flowpath extending from the secondary flowinlet to form a combined flowpath to the outlet, wherein from upstreamto downstream along the motive flow flowpath, the motive nozzle has: aconvergent section; a throat; and means for providing an a secondacceleration upstream of the motive nozzle exit that is lower than afirst acceleration downstream of the throat.
 20. The ejector of claim 19wherein the means comprises; a first divergent section; and a seconddivergent section, the second divergent section diverging at a shallowerangle than the first divergent section.